In the processing of foods, generally there have been two approaches to the packaging of food product in a container. The first method utilizes retorting, whereby a food product is placed into a container, the container is sealed, and then the product and container are subjected to heat such that the product is sterilized. In the second method, a container is subjected to a sterilizing process prior to its receiving sterilized food product.
Conventional processes for sterilizing containers in which food stuffs are subsequently packaged include UV irradiation, treatment with a mixture of steam and air, and an aseptic technique in which the interior wall of the container is sprayed with liquid hydrogen peroxide and subsequently dried.
An example of an apparatus and method for sterilizing containers by means of treatment with steam is disclosed in U.S. Pat. No. 4,494,363 issued to Rica, et al. This method and apparatus for aseptically filling containers discloses an automatic, as opposed to manual, filling system.
Experience has shown peroxide to be a particularly reliable sterilizing agent for killing micro-organisms. The germicidal action of peroxide depends upon the formation of the hydrogen peroxide free radical and the formation of free oxygen. The free oxygen being formed during thermal decomposition of H.sub.2 O.sub.2 and exhibits a particularly strong sterilizing affect at the moment of formation. The efficiency of the wet aseptic process is attributable to the liquid hydrogen peroxide being able to penetrate the cell walls of micro-organisms.
Since hydrogen peroxide is a chemical irritant, it is necessary to obtain residual levels of less than 0.5 ppm (parts per million) before contact with product. The removal of the peroxide is typically achieved by evaporation, and thus a wet aseptic process requires, subsequent to the spraying step, a heating step. For example, the apparatus for the aseptic packing of high acid food disclosed in U.S. Pat. No. 4,409,775 issued to Brody, et al. dries the container by drainage and evaporation.
However, under the best of circumstances, (i.e. with the finest nebulization) uniformity of droplet distribution is not always possible for the internal surface of a container. The inability to completely wet the surface of the container during peroxide spraying can be attributed to the fact that droplets form on the surface and unwetted areas remain between these droplets. As a result, the combined spraying and heating steps associated with the wet aseptic process may not result in absolute or complete sterilization of the entire internal surface of a container.
A process for sterilizing tub shaped containers utilizing hydrogen peroxide vapor is disclosed in U.S. Pat. No. 4,424,199 issued to Hick. The vaporization is preferably achieved by spraying the sterilizing agent onto a heating element which is positioned either in or immediately above the open top of the container. The apparatus is configured to preclude the presence of vapor outside the immediate environ of the container to be sterilized, as well as limiting sterilization to one specific configuration of container.
Another problem with aseptic technology is that it is important to find out how a product behaves when it is sterilized aseptically. It is also important to see how the proposed container, typically a plastic container, reacts during and after aseptic process sterilization. Currently, it is necessary to purchase a production piece of equipment dedicated to one type of container, one type of container size, one type of operation, and one type of product. These units typically cost well above $1,000,000 which constitutes a considerable investment in terms of basic research.
It is thus apparent that the need exists for an improved apparatus and method for aseptic packaging which permits an extremely effective microbial kill while being sensitive to operating costs. It is also apparent that the need exists for an improved research tool associated with aseptic process sterilization which permits research on aseptic process sterilization at a relatively minimal cost, with this research tool having the capability to evaluate multiple containers and multiple sterilization treatments.